This invention relates to recovery of the constituents of poly(arylene sulfide) in reaction slurries. In accordance with one aspect of the invention it relates to the recovery of polar organic diluent from a poly(arylene sulfide) reaction mixture. In another aspect of the invention, it relates to the recovery of poly(arylene sulfide) from its reaction mixture. In still another aspect of the invention, it relates to the atmosphere adiabatic evaporation of diluents from a mixture of reaction mixture with steam.
In one of its concepts, the invention relates to the adiabatic atmospheric evaporation of polar organic diluent from a mixture of a reaction effluent with steam added to reduce the dew point of the reaction diluent as an aid to evaporation. In another of its concepts, the invention relates to separation of a poly(arylene sulfide) compound from its reaction mixture by evaporation of the diluent from the mixture prior to filtering in order to obtain a more readily processable particulate polymer.
A poly(arylene sulfide) must be relatively free of metal halide salts and other ash producing contaminants to be of full usefulness and value. A major problem in the production of poly(arylene sulfide) has been the recovery of high purity polymer from the contaminants in its reaction mixture. It was discovered early in the commercial production of poly(arylene sulfide) that the polar diluents usually used in polymerization processes caused difficulty in separating the polymer from its mixture by such usual means as filtration in that the diluent and polymer produces a filter cake of such "pasty" physical characteristics that plugging of the filter is a continuous problem and washing the filter cake free of other contaminants is impossible. To avoid these problems, methods have been proposed for removal of the diluent from the polymer before separation of the polymer and other contaminants is attempted. Methods of vacuum evaporation of the diluent have proved successful in separating the diluent and polymer to produce a slurry filter cake that can be reslurried and filtered to remove metal halide salts and other contaminants. It has now been found that by mixing the reaction slurry with a high pressure steam and concurrently reducing the pressure on both streams the dew point of the polar diluent can be reduced sufficiently to permit flashing of more than 75 percent of the polar diluent from the reaction slurry mixture.
Accordingly, it is an object of this invention to provide an economical method for recovering polar diluent from the reaction mixture of a poly(arylene sulfide) reaction. It is another object of this invention to provide an integrated method and apparatus for the recovery of poly(arylene sulfide) and contaminant solids free of polar diluent.
Other aspects, objects and advantages of this invention will be apparent to one skilled in the art upon studying the specification, drawing and the appended claims.